Short answer: Gnome.
It has been a few years since I tried using a XWindows desktop, and I thought it was time to see where they stood. After doing a Google search of "gnome vs kde", I found a few articles that said about the same thing: "Gnome is more mature, KDE is a bit less stable and flashier". That sounded believable, so I installed current Ubuntu (which, fortunately for Ubuntu users, comes with Gnome) and Kubuntu (a parallel distribution that comes with KDE).
The reviews were correct: KDE is less stable and flashier. In this case, "flashier" means "useless chrome and cutesy application naming that do not help get real work done".
The KDE folks clearly have not thought this through for typical users. For example, I wanted to change my network settings:
Note that there is no "Administrator Mode button". That's because the window by default comes up with the button (which is at the bottom of the window) not visible, with no indication that the window was resized to cut off the bottom. Gnome doesn't have this kind of lameness; as far as I can tell, you can't resize a window in a way to hide active items.
I'll go with "mature".